JONESBORO (AP) — Investigators in Jonesboro may never determine why a man recently released from a mental health facility killed three people and wounded four others before fatally shooting himself, the town's police chief said.

Police accuse Porfirio Hernandez, 40, of shooting six people — including three children — at a Jonesboro home Saturday, then driving to a business and fatally shooting another man. Hernandez was found dead of a self-inflicted gunshot wound later Saturday, Jonesboro Police Chief Mike Yates said Sunday. Yates said Hernandez had been released from a mental facility a few days before Saturday's shooting but that investigators don't know why Hernandez was being treated.

"We may never have a concrete motive for this," Yates said. "He sought help for something."

Police responded to the shooting at the Jonesboro home at about 1 p.m. Saturday. Chrisanto Islas, 38, and Floza Davila, 12, were killed there and four others were injured. Survivors and witnesses at the house identified Hernandez as the sole gunman and provided a description of him and the vehicle he was driving, police said.

Police said three people are in critical condition in hospitals in Memphis, Tennessee: Augusten Hernandez, 43; Ayde Davila, 36; and Anquel Islas, 8. A 10-year-old boy, Brayam Davila, is in stable condition.

Police said Sunday that Hernandez was an acquaintance of the victims.

Retired postal carrier Steve Moore, who lives near the home where the six shootings occurred, said the victims were good neighbors.

"They were better than any neighbor I ever had," Moore said. "They'd keep an eye on our place when we were away. We'd look out for each other. We've never even had a cross word — even with their guests. They've all been just as nice as they can be."